This specification relates to electromagnetic communications.
Advances in semiconductor manufacturing and circuit design technologies have enabled the development and production of integrated circuits (ICs) with increasingly higher operational frequencies. In turn, electronic products and systems incorporating high frequency integrated circuits are able to provide greater functionality than previous generations of products. The additional functionality has typically included the processing of increasingly larger amounts of data at increasingly higher speeds.
Conventional contactless communications use a carrier signal to transmit information through space as an electromagnetic wave. The carrier signal is typically modulated with an input signal to carry information. A carrier signal can be modulated in a number of ways. In digital modulation, an analog carrier signal is conventionally modulated by a discrete signal.
One conventional modulation technique includes modulating the phase of the carrier signal. Phase-shift keying (PSK) is a digital modulation that uses a finite number of phases, each assigned a unique pattern of binary digits of the input signal. Typically, each phase encodes an equal number of bits. Each pattern of bits forms a symbol that is represented by the particular phase.
The simplest form of PSK is binary PSK where the phase change can be either 0 or 180 degrees. That can be mapped to a binary sequence where for instance a “1” corresponds to a 180-degree phase shift while a “0” to 0 degree or no phase shift.
To recover the information at a receiver, a demodulator is used to extract the input signal from the modulated carrier signal. PSK demodulation determines the phase of the received signal and maps it back to the symbol it represents to recover the original information. Conventional PSK demodulation requires the receiver to be able to compare the phase of the received signal to a reference signal synchronous with the carrier signal.